The invention pertains to a process and an apparatus for the production of labeled plastic bottles.
In the production of labeled plastic bottles it is known (DE-AS 17 04 022), to first continuously produce plastic bottles from blanks in a blowing machine. Blowing machines of this kind take the preheated blanks, also called preforms, into specially designed blow molds, in which they are blown into bottles at high pressure and high temperature during the rotation of the blowing machine. At the outlet of the blowing machine the bottles are then passed on to an output star wheel.
In this method known in the art, the bottles, once ready, are passed on from the output star wheel to a filling machine, which operates in a rotary manner as well. There the bottles are filled with the desired liquid. Then the bottles are capped by a bottle capping machine and passed on to a labeling machine. The disadvantage of this system is that it is not always possible to ensure that the outside surface of the bottle, which will be labeled, stays dry and clean during the filling and capping procedure, which is an essential precondition for reliable labeling.
It has also been proposed (DE-OS 26 21 993) to pass on the bottles from a blowing machine to a carousel in a clocked manner, and to perform different treatment steps intermittently in this carousel, that is to say first a testing procedure, then the labeling, then the printing, then the filling and then finally the capping and the packaging. The disadvantage here is that this clocked operation does not allow for high output rates.
It is the task of the invention to provide a process and an apparatus, by means of which labeled plastic bottles can be produced at high capacity and with a nonetheless reliable label hold.
In the process according to the invention, the plastic preforms, after having been continuously created in a blowing machine, preferably in a rotary blowing machine, are then continuously labeled without the interposition of any further treatment steps and directly afterwards, i.e. downstream from the blowing machine, whereby only the pitch distance has to be adjusted to the distance required for labeling, if necessary. The advantage of this is that by means of the immediately consecutive arrangement of the blowing and labeling procedure it can be ensured that the bottles, leaving the blowing machine absolutely dry and clean, are labeled directly afterwards, so that the label can be attached reliably on a clean surface. The continuous operation, as opposed to a clocked operation, allows for substantially greater bottle output per hour, and consequently for a greater capacity of the system.
In an advantageous embodiment of the process, the bottles, after leaving the blowing machine, are passed on to an output star wheel, where they are set at the pitch distance required for labeling. Preferably, to implement this step, an output star wheel is used which has controllable gripper arms for the bottles which allow for modifying the distance between the consecutive bottles. Such transporter stars are known in the art (for example DE-OS 3837 118, to which express reference is made here). Despite continuous operation, such proceeding saves a lot of space and provides for an efficient blocking of the blowing and labeling machine, since the output star wheel can at the same time be used as the input star wheel for the downstream labeling machine.
An output star wheel without pitch distance control, however, can also be used. In this case, a downstream distancing worm screw can be used, if necessary.
More than ever, the advantages of the invention become noticeable when a label preformed as a sleeve has to be pulled over the bottles in the labeling machine. A heat shrinking tubular foil or a stretch foil is usually used for these so-called sleeve labels, from which foil sleeve shaped sections are prepared. The sleeve diameter is selected to be only slightly wider then the diameter of the bottle in the area, where the label will be attached. If the bottle is clean and dry, there are no problems with adhesion of the foil in moist spots or similar during the pulling process, rather, the sleeve label can be attached very easily and troublefree. Afterwards the label is fixed to the bottle by exposure to heat or mechanical shrinking due to earlier stretching.
It is also possible to utilize the invention in conjunction with a labeling unit which attaches labels to bottles in a traditional way, for example by gluing the whole surface or part of it.